Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

244 Chapter 9 Mass and Mass-Related Parameters

After 5 minutes,

and the time that is required to fill the tank (b)

Example 9.4 We are interested in determining the mass-flow rate of fuel from the gasoline tank of a small

car to its fuel injection system. The gasoline consumption of the car is 15 kilometers per liter

when the car is moving at the speed of 90 km/h. The specific gravity of gasoline is 0.72. If

there were one million of these cars on the road, how many kilograms of gasoline are burned

every hour?

First, we will use Equation (9.2) to compute the density of gasoline.

The volume-flow rate of fuel for a single car is determined from:

• 
  

Next, we will use Equation (9.6) to calculate the mass-flow rate of the fuel.

mass-flow rate(density)(volume flow rate)

mass-flow

Each car burns 4.32 kg /h, so for one million cars in each hour 4,320,000 kg of gasoline is

burned!

Summary

Now that you have reached this point in the text

• You should have a good understanding of what is meant by mass and know about the im-
  portant roles of mass in engineering applications and analysis.


• You should know that in engineering to show how light or heavy materials are, we use prop-
  erties such as density, specific volume, specific weight, and specific gravity. You should also
  know the formal definition of these properties.

ratea 720

kg

m

3 ba^6

liter

h

ba

1 m

3

1000 liters

b4.32 kg/h

flow rate

90 km/h

15 km/liter

volume 6 liter/h

SGgasoline0.72

density of gasoline

1000 kg/m

3 Sdensity of gasoline^720 kg/m

3

time required to fill the tank

12000 kg

31 2 kg/s 2  1 1 kg/s 24

12000 s200 min

300 kg

change of mass inside the control volume 31 2 kg/s 2  1 1 kg/s 241 5 min2a

60 s

1 min

b

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